[floh-jis-ton, -tuhn]
a nonexistent chemical that, prior to the discovery of oxygen, was thought to be released during combustion.

1720–30; < Neo-Latin: inflammability, noun use of Greek phlogistón, neuter of phlogistós inflammable, burnt up; see phlogistic Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
phlogiston (flɒˈdʒɪstɒn, -tən)
chem a hypothetical substance formerly thought to be present in all combustible materials and to be released during burning
[C18: via New Latin from Greek, from phlogizein to set alight; related to phlegein to burn]

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Word Origin & History

1730, "hypothetical inflammatory principle," formerly believed to exist in all combustible matter, from Mod.L. (1702), from Gk. phlogiston (1610s in this sense), neut. of phlogistos "burnt up, inflammable," from phlogizein "to set on fire, burn," from phlox (gen. phlogos) "flame, blaze" (see
bleach). Theory propounded by Stahl (1702), denied by Lavoisier (1775), defended by Priestley but generally abandoned by 1800.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
phlogiston   (flō-jĭs'tən)  Pronunciation Key 
A hypothetical colorless, odorless, weightless substance once believed to be the combustible part of all flammable substances and to be given off as flame during burning. In the 18th century, Antoine Lavoisier proved that phlogiston does not exist. See Note at Lavoisier.
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Encyclopedia Britannica


in early chemical theory, hypothetical principle of fire, of which every combustible substance was in part composed. In this view, the phenomena of burning, now called oxidation, was caused by the liberation of phlogiston, with the dephlogisticated substance left as an ash or residue.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
To this layman it is beginning to smell of phlogiston.
Once upon a time not too long ago everyone knew for a fact that there was phlogiston and an aether.
Uses the overthrow of the phlogiston theory to provide students with insight into the nature of science and changes in theory.
It took a hundred years to give up the idea of phlogiston.
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